Tensile Strength of Concrete

The axial tensile strength of concrete is very less because concrete is a heterogeneous mass, and every heterogeneous mass is weak in tension and strong in compression. But there is some indirect method to find the tensile strength of concrete.
A structure was designed based on the compressive strength of concrete. Therefore, most of the time, the tensile strength of concrete tests is not required to be performed on-site. The framed structure consists of a combination of brittle and ductile materials.
Brittle material – concrete, Ductile material – Reinforcing concrete has good compressive strength and low tensile strength. Then reinforcement was provided in the concrete to prevent cracking.
They are as follows.

Table of Contents

Flexural Tensile Strength (Modulus of Rupture)

A beam of size 500mm x 100mm x 100mm is cast and two equal loads of W/2 is placed on both side from the center at a distance of 200mm and flexural strength in tension is calculated.
As per IS456 clause 6.2.2 flexural strength $f_{cr}=0.7\sqrt{ck}$

Where $f_{ck}$ is characteristic strength of concrete in $N/MM^2$ and $f_{cr}$ is known as modulus of rupture in $N/MM^2$

Spilt tensile strength

It is an indirect method of determining the tensile strength by applying a compressive force on a cylinder having 300mm length and 150 mm dia. Force applied is compressive but failure takes place in the lateral direction in tension. (poison‘s effect).

$f_{ct} =\frac{2F} {\pi ld}$
Where $f_{ct}$ is spilt tensile strength of concrete

$f_{ct} = \frac{2}{3} *f_{cr}$

Where, $f_{ct}$ is spilt tensile strength in $N/MM^2$ and $f_{cr}$ is known as modulus of rupture in $N/MM^2$

Direct tensile strength

The tensile strength of concrete, measured from spilled tensile strength is near to the true tensile strength of concrete than the modulus of rupture. But it is difficult to measure.

$f_{cd} =0.5* f_{cr}$